Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a nacelle, a rotor, a generator, and a gearbox. The rotor typically includes a rotatable hub and one or more rotor blades. The rotor blades capture kinetic energy from wind using known airfoil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
A wind turbine and its components must be designed to withstand various loads experienced during operation. The term “component” or “components” when discussed herein in reference to a wind turbine is defined as any wind turbine feature, including, but not limited to, the tower, nacelle, rotor, generator, gearbox, hub, shaft, rotor blade, pitch bearing or drive, yaw bearing or drive, generator frame, bedplate, foundation, or any portion of the wind turbine that may experience a load.
Wind turbine components are typically designed based on simulations representing several events that might occur during the life of the wind turbine, including, but not limited to, wind speed, wind gusts, turbulence intensity, or any other event which causes a load to act on the wind turbine or its components. These events may vary at different wind farm sites; therefore, a safety factor is typically included with the design loads of individual wind turbine components to ensure that catastrophic failures are minimized during an extreme event or random loading condition. Such safety factors, however, generally provide an excess design margin, causing individual wind turbine components to be over-designed. At any given time during the life of the wind turbine, the components are not operating at their design envelopes and there is extra component design margin left, resulting in the components performing below their maximum load capacity during their lifetime.
Many modern wind turbines utilize real-time or asymmetric load control (ALC) systems to control and enhance wind turbine component operation. For example, real-time and/or ALC systems use proximity sensors or strain gages (or combinations of both) to constantly monitor loads at the hub center, and to keep these hub center loads within setpoint limits through blade pitching. These ALC loads are not, however, directly linked to the limiting design loads of the individual components. The setpoint load limits are generally selected to incorporate the safety load factors discussed above to mitigate unforeseen events. With conventional ALC load control methodologies and systems, the wind turbine generator is being under-utilized.
Accordingly, an improved system and method for load control of a wind turbine that utilizes the inherent increased capacity of the various wind turbine components to increase overall performance and output over the life of the wind turbine would be desired in the art.